My invention pertains to apparatus for determination of the capacity value of capacitors used in commercial electrical equipment.
In the commercial electrical industry, capacitors are extensively used with alternating current power systems and alternating current motors. It is frequently necessary to verify and/or determine the capacity value of a capacitor prior to its installation and use.
Determination of capacitor value by measurement of alternating current flow through the capacitor follows basic electrical principles. The Williams U.S. Pat. No. 2,455,543 discloses application of a direct current that alternately charges and discharges the capacitor to obtain a current flow measurement. Sharland U.S. Pat. No. 2,135,017 and Marlow U.S. Pat. No. 3,320,527 disclose tapped coils to, in effect, produce a plurality of coils.
Available equipment for capacity determination is elaborate and complicated for use by the conventional electric shop. Capacitor testers employing electrical bridge circuits are delicate and require detailed knowledge to obtain acceptable results. Such equipment requires the use of electrical formulae in determination of the capacitor value.
It is the general objective of my invention to provide simple apparatus available to the electric shop that permits capacity value determination by use of normally available alternating current and a conventional tong-type alternating current ammeter by application of simple multiplication of the ammeter reading by a predetermined factor to determine the capacitor value.
Another object of this invention is to provide apparatus that is rugged in structure.
Another object of this invention is to provide apparatus that is simple in construction.
Another object of this invention is to provide apparatus that is readily transported to the point of use.
Another object of this invention is to provide apparatus that is low in initial cost.
Another object of this invention is to provide apparatus that is of long life.
Another object of this invention is to provide apparatus that will withstand electrical abuse.
Another object of this invention is to provide apparatus that is efficient and reliable.
Another object of this invention is to provide apparatus that is accurate within the limits normally required.
Another object of this invention is to provide apparatus that assures freedom from electric shock by the equipment being tested.
Broadly considered, the foregoing and other objects are accomplished by apparatus that comprises at least one, preferably a plurality of individual coils of differing numbers of turns, forming a toroid permitting insertion of the tongs of a conventional tong-type alternating current ammeter for measurement of current flow. Each coil provides an electrical circuit between a pair of power leads and a pair of test leads to which the capacitor being tested is electrically connected. Each circuit consists of a coil and a switch permitting selection of the coil through which current flows to energize the capacitor under test to obtain an ammeter reading related to the current flow through the selected coil. An independent switch provides momentary shorting of the test leads through a coil or a resistor to discharge the capacitor following the test. The switches and all electrical connections are contained within a box having the power cable and test leads extending therefrom and having the toroid mounted externally on the box to receive the ammeter tongs. Each switch is designated by the multiplier to be applied to the ammeter reading to obtain the micro-farad value of the capacitor under test.